Dashboard Disappeared, Log-In Loop

I’m having an issue with a fairly new install of WordPress. I’ve installed WordPress numerous times on different servers and have never come across this particular problem and it’s driving me batty trying to find the culprit. Anyone’s help would be most appreciated!

I successfully installed WordPress, set-up my theme, added my pages, posts, etc. Everything was working fine, no issues and the site went on as normal. Then suddenly while in the middle of editing a page (nothing fancy, no setting or theme changes), I was logged out of WP. I went to log back in and suddenly my Dashboard doesn’t come back up – I merely get an index page (Index of //wp-admin) listing the contents of the wp-admin folder. At first I was able to still click any of the links there to access the Edit pages directly and I went about finishing my edits on the pages because the site itself still loads without issue.

Then POOF, suddenly I can’t access these pages either. Every link leads to a re-authorization to log-in but entering the proper username/password simply leads back to the log-in page. Rinse and repeat. Going to https://www.URL.com/wp-admin/ still leads to the index listing (Index of //wp-admin)

And then slowly but surely, my pages stopped working on the site. One after the other just didn’t load up (file not found on server, not a 404 error).

At this point, I deleted all my WordPress files and uploaded new ones from a fresh download of the newest version. Same problem. I deleted my .htaccess file, reset the site URL in my wp-config.php – nothing helped. I’ve now had to replace the WordPress site with static PHP pages until I can find out what happened to WordPress.

Any thoughts? I’ve searched for answers but my problems seem to be all over the place. Could it be possible to have a hack so soon in an install? Some corruption somewhere? Any ideas helpful – thanks!